Studies of $$\mathrm B ^*_\mathrm s2(5840)^0$$Bs2∗(5840)0 and $$\mathrm B _\mathrm s1(5830)^0$$Bs1(5830)0 mesons including the observation of the $$\mathrm B ^*_\mathrm s2(5840)^0 \rightarrow \mathrm B ^0 \mathrm K ^0_\mathrm S$$Bs2∗(5840)0→B0KS0 decay in proton-proton collisions at $$\sqrts=8\,\text TeV$$s=8TeV